They both produce bits of flying gore and blood, but in the final analysis, it MUST be the baby.
The chainsaw requires a clumsy grip with the hands at near-perpendicular angles. This will naturally diminish the velocity of any stroke. A baby, OTOH, you can simply grab by the ankles, toss over your shoulder and bring forward and down in one Kubrickian-cathartic moment of impact-based ecstasy. Bliss.
:malirams